The control scheme in this converter is a constant on-time control which sets the on-time to a fixed value while extending the off-time to reduce current below the limit. This valley current limit control senses the low-side switch current to keep the on-time constant and to extend the off-time, reducing current below this limit (1.1A).
The device features a robust overcurrent protection scheme that also protects the device and inductor under overload and output short-circuit conditions. A cycle-by-cycle peak current limit turns off the high-side MOSFET and turns on the low-side MOSFET whenever the high-side MOSFET current exceeds the internal peak current limit (3A). The low-side MOSFET remains on until the inductor current reduces to the valley current limit (1.1A). After that, the high-side MOSFET is turned on again and the cycle repeats.